Temperature dependence of one-dimensional motion of interstitial clusters in Fe and Ni

The temperature dependence of one-dimensional (1-D) motion of interstitial clusters and void growth in Fe and Ni was studied to a dose of 0.3 dpa. Two criteria were applied to detect the 1-D motion of interstitial clusters. One is the formation of interstitial type dislocation loops near the dilatational side of edge dislocations. The other is no formation of interstitial type dislocation loops near grain boundaries. In neutron irradiated Ni with improved temperature control at 573 K, the 1-D motion of interstitial clusters existed. However no evidence of 1-D motion was found for a conventional temperature controlled irradiation, where the specimen temperature changed with reactor power. This suggested that there was little 1-D motion of interstitial clusters at lower temperatures during the start-up of the reactor. In neutron irradiated Fe, the 1-D motion of interstitial clusters occurred at 473 K and 623 K, judging from the criteria. A good correlation existed between the 1-D motion of interstitial clusters and void growth. These results are discussed based on the temperature dependence of the interaction between impurities and interstitial clusters.